There are many devices for delivery of medicament that have been developed for self-use, i.e., that the patient or other non-medically trained persons handles the device during medicament delivery. Such devices comprise inhalers, nebulizer and injectors. For many treatments, like asthma, diabetes, hormone growth, the patient has to receive doses on a regular basis and the advantage with such devices is that the patient can administer the delivery anywhere and is not bound to visit care facilities in order to receive medication.
The self-medication devices need to both reliable and easy to use for an untrained user. It is thus necessary that the risks of wrong handling of the device are minimized so that the user cannot receive wrong dose sizes.
A number of devices have the possibility of setting a certain dose size, which size depends on the actual patient and the treatment and where the device is capable of delivering a number of doses before the medicament in the device is finished. However for many patients and treatments the same dose size is to be set for every delivery. In these aspects it is also important that the dose cannot be set too high, which otherwise could cause serious consequences. Especially for children that are to self-administer medication, it is a safety aspect for the parents and the physician that the dose cannot be set too high.
Another problem of trying to limit the maximum allowable dose is with devices where the dose setting mechanism can be turned more than a full turn in order to set a dose. In devices of this kind it is difficult to arrange a dose stop by other means than a feature standing in the way for a rotation required to drive a piston so that a dose is provided, or relying on the spring in use to expand towards where a force no longer is exerted. In the first case one could be limited to doses that can be set within principally one turn of a dose knob.